I was wondering if there was a way to check and deny a user from entering the same information as another user for customer user fields. I don't want two users to enter the same username (save myself some on site drama) for specific fields like AIM, YIM, ICQ, XBOX, PSN, STEAM, and the list goes on. I feel this is already built into the site since at user registration it checks to see if a username/email is already taken. Do I use a php callback??? is there some option I'm not seeing? Thanks in advance for any help.